IT Baseline Protection Manual - The Information Warfare Site

Safeguard Catalogue - Communications Remarks
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originator identifier (CSID) is not disguised or, where ISDN is used, if the
originator does not withhold his call number. If it is not possible to determine
the originator's fax number, the only remaining option is to expand the
existing capacity, as described above.
Another potential problem with a fax server is hard disk capacity. The danger
that an adversary will deliberately exhaust the hard disk capacity through an
attack is slim. A single faxed DIN A4 page occupies around 70 KB. Given
that most hard disks today hold several gigabytes, when one considers the
telephone charges that would be incurred, an attack of this kind is improbable.
Generally, all incoming and outgoing fax transmissions are stored either
permanently or temporarily on the hard disk of the fax server. What happens
then depends on the faxed server application and possibly on the configuration
as well. One possibility is that all faxed transmissions are permanently stored
or archived on the hard disk of the fax server. When this mode of operation is
employed, depending on the volume of faxes, it is possible for the hard disk
capacity to quickly become exhausted. In this case steps should be taken to
ensure that outgoing fax transmissions and incoming faxes which have already
been read are archived as soon as possible on external data media and deleted
from the fax server. To achieve this result, the amount of memory placed at
the disposal of users on the fax server should be limited. In addition, an SOP
should be issued to the effect that fax transmissions which are no longer
required are to be deleted. This applies especially to unsolicited advertising
material received. Regular checks of the amount of free storage space on the
fax server's hard disk should be performed by the fax mail centre.
Additional controls:
- At what times is the fax server heavily loaded?
- Are there any standard operating procedures in place restricting the
sending of faxes at busy times to urgent cases?
- Is permanent archiving of faxes not performed on the fax server?
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IT-Baseline Protection Manual: Oktober 2000
Ensure hard disk has
sufficient space